# Field, power, and root-power quantities

A **power quantity** is a power or a quantity directly proportional to power, e.g., energy density, acoustic intensity, and luminous intensity.^{[1]}

A **field quantity** is a quantity such as voltage, current, sound pressure, electric field strength, speed, or charge density, the square of which, in linear systems, is proportional to power.^{[2]} The term **root-power quantity** was introduced in the ISO 80000-1#Annex C, defined as the square root of a power quantity; it replaces and deprecates the term *field quantity*.

## See also

- Fresnel reflection field and power equations
- Sound level, defined in different ways for the pressure or power of sound

## References

- ↑ Ainslie, M. A. A Century of Sonar: Planetary Oceanography, Underwater Noise Monitoring, and the Terminology of Underwater Sound. Acoustics Today (2015)
- ↑ Brian C.J. Moore (1995).
*Hearing*. Academic Press. p. 11. ISBN 9780080533865.

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